A trend emerging in computer system development and manufacturing involves a move toward a building block-based approach, where a system is created by a collection of building blocks. This approach places increasing need on the ability to detect, enable/disable, and customize building blocks to create the desired personality of the system.
The flexibility of varying the system configuration through building blocks requires that the POST (power-on self test) of the planar be able to detect, enable/disable, and configure the various options installed. This is frequently handled with the use of General Purpose Input Outputs (GPIOs). Typically, a GPIO can only detect two states (high/low) and is dedicated to a function or a particular device. For example, if a particular card is installed, the GPIO may detect a low state, while if the card is not installed, the GPIO may detect a high state.
The push to a building block model is rapidly increasing the need for GPIOs to assist in the detection of the building blocks installed. However, some systems have to limit the number of GPIOs due to other design considerations. Thus, a need exists for a manner of increasing the amount of control information from GPIOs without increasing the number of GPIOs.
The present invention addresses such a need.